Side-fire helical antenna with conductive support



Nov. 27, 1962 1.. o. KRAUSE ETAL 3,066,295

SIDE-FIRE HELICAL ANTENNA WITH CONDUCTIVE SUPPORT Filed April 16, 1959FIG.1

FIG?) INVENTORS Lloyd QKrause [I n BY Ronald E. Fisk TRANSMITTER AT TOREY 3,85%,295 Patented Nov. 2?, i962 3,066,295 SIDE-F HELICAL ANTENNAWITH CGNDUCTIVE SUPPORT Lloyd 0. Krause, North Syracuse, and Ronald E.Fisk,

Liverpool, N.Y., assignors to General Electric Company, a corporation ofNew York Filed Apr. 16, 1959, Ser. No. 806,838 21 Claims. (Cl. 343-874)This invention relates to antennas of the kind used for the radiationand reception of electromagnetic energy and more particularly toantennas for radiating and receiving high frequency energy having abroad azimuth directivity and wide bandwidth.

In many communication and television applications, there is a need forradiating electromagnetic energy from a central source to a plurality offixed or mobile receivers at any azimuth position about the centralsource. The radiation should be omnidirectional to permit the uniformdistribution of the radiant energy to all points in circles concentricwith the central source. Such a distllblltzOl'l affords the efiicientutilization of the available electromagnetic energy when the receiversare uniformly distributed over a given area or when the mobile receivershave equal probabilities of being at any position within the area.

Although antenna systems are available which are substantiallyomnidirectional, their radiation efliciency is limited by the spread inthe elevation distribution of the electromagnetic energy. The elevationdistribution may be defined as distribution in planes normal to thesurface of the earth. When communication antenna systems transmit lineof sight range signals, i.e., PM. or television, most of theelectromagnetic radiation transmitted in directions above the horizon isincapable of reception and therefore wasted. To minimize the amount ofunavailable radiation transmitted by such antenna systems, it isnecessary to decrease the angular spread of the radiation elevationdistribution.

Many techniques employing complicated arrays and stacks have beenemployed in obtaining more desirable elevation directivitycharacteristics. The resultant antenna systems are usually complex andexpensive. However, very satisfactory solutions for the problem areobtained by using the side-fire helical antennas described and claimedin the following copending United States applications: Lloyd 0. Krauseand Howard G. Smith, Serial No. 732,482, filed May 2, 1958, now PatentNo. 2,985,878; Paul M. Pan, Serial No. 646,837, filed March .18, 1957,now Patent No. 3,019,438; and Lloyd 0. Krause, Serial No. 739,748, filedJune 4, 1958, now Patent No. 2,953,786; all of which are assigned to thesame assignee. Each of the helical antennas disclosed in the citedapplications has a cylindrical central conductor with a helicalradiating conductor disposed, with a radial separation, about thecylindrical central conductor. A radiating conductor is one which iscapable of radiating electromagnetic energy when it is coupled to asource of such energy.

These side-fire helical antennas have stimulated a demand for evenbetter antennas of the same type. In particular, even through thebandwidth of these antennas is unusually broad for their type, it hasbeen found that greater bandwidths are desirable in some applications.For example, the lower channels of VHF television transmission requirelarge percentage bandwidths with channel 2 requiring a twelve percentbandwidth. Furthermore, these antennas may be considered as unterminatedradiating transmission lines which because of their length and radiatingconductor to central conductor spacing cause controlled radiation andattenuation of the energy propagated along the line. Presently, toprovide such bandwidth it is necessary to use a higher rate of attenuation per turn with fewer turns and resulting lowered verticaldirectivity. Thus, fewer than the optimum number of turns must be used.

It is accordingly a general object of the invention to provide animproved antenna.

It is a more specific object of the invention to provide an improvedhelical antenna which has a high radiation etficiency together with avery broad bandwidth.

It is another object of the invention to provide an improved helicalantenna of the side-fire type which is more adaptable in certainapplications than previous helical antennas.

Briefly, in accordance with a general aspect of the invention, anantenna is provided comprising a central conductor and a radiatingconductor. The central conducior has a polygonal cross-section. Theradiating conductor is developed about the central conductor as a seriesof axially progressive turns which are radially spaced from the centralconductor. A first energization terminal is coupled to the cenlralconductor and a second energize.- tion terminal is coupled to theradiating conductor. The energization terminals are adapted to receivesignal energy for radiation by the radiating conductor.

It should be noted that there is a discontinuity in the spacing betweenthe radiating conductor and the central conductor at each vertex of thepolygon. This discontinuity is electrically equivalent to a lumpedreactance across the equivalent transmission line. Thus, at each vertexthere is a discontinuity loading effect. Furthermore, it should be notedthat when each turn of the radiating conductor is substantially anintegral number of operating wavelengths and the polygon is regular theloading is periodic. This periodic loading causes a dispersive phasevelocity with a frequency characteristic having a positive slope. Hence,the turn to turn phase remains in substantial equality over a widerfrequency range, thus giving increased operating bandwidth for a givennumber of turns and atienuation per turn. Hence, a more optimum numberof turns for a given application may be used. In some cases, it may bedesirable to add additional periodic loading by the addition of metallicor insulative discontinuities.

The major mode of energy transmission of a side-fire helical antennafollows the path traced out by the radiating conductor. It is this majormode which causes the antennas to side-fire radiate in azimuthallydistributed patterns with a minimum of elevation distribution. However,these antennas may also be considered to be degenerate forms of coaxialtransmission lines with the central conductor of the antenna serving asthe central conductor of the coaxial transmission line and the radiatingconductor serving as a discontinuous outer conductor of the coaxialtransmission line. Thus, there is a minor mode of energy propagationwhich coaxially travels along the antenna. This minor mode does notradiate and attenuate. Therefore, it determines the limit of isolationbetween the feed and other end of the helix. Thus it limits the ease anddegree of self-diplexing or dual-feeding of the antenna.

It is accordingly an object of another aspect of the invention toenhance the performance of helical antennas of the side-fire type whenused in self-diplexed applications.

It is another object of this aspect of the invention to provide aside-fire helical antenna which has. a minimum of coaxially propagatedenergy.

Briefly, in accordance with this aspect of the invention, an antenna isprovided comprising a ribbonlike conductor extending along the axis ofthe antenna as a plurality of axially progressive turns. A radiatingconductor is further provided which extends along the axis of theantenna as a plurality of axially progressive turns. The radiatingconductor is radially displaced from the ribbonlike conductor with eachelement of the radiating conductor radially projectable on theribbonlike conductor. First and second energization terminals arerespectively coupled to the ribbonlike conductor and the radiatingconductor, and adapted to receive signal energy for'radiation by theradiating conductor.

A feature of this aspect of the invention is the construction of theribbonlike conductor from a substantially flat mesh of conductors.

It should be noted that the use of a ribbonlike mesh of conductorsfurther limits the propagation of the minor coaxial mode to furtherincrease the isolation between the energization terminals and the endsof the antenna. Therefore, such an antenna can more easily be of theself-diplexing type. That is, two separate signals can be simultaneouslyfed to the same radiatable conductor for radiation. One signal is fed toone end of the radiating conductor and the other signal is fed to theother end of the radiating conductor. Such a system is highlyadvantageous in television transmission where the auralsignal and thevideo signal are simultaneously transmitted. The two signals remainessentially isolated from each other.

In addition to the electromagnetic advantages gained, there are alsomany mechanical advantages. In the lower frequency channels oftelevision transmission the required size of the antennas is quitelarge. Since the antennas must be elevated to insure uniform signalreception, it is necessary to support these antennas on very tall masts.However, when the antennas of the invention are employed the mechanicalload borne by the mast is much less and, in fact, the mast may beconsidered as part of the antenna. Furthermore, since the antennas ofthe invention are skeletal in nature, i.e. there is a min imum ofcontinuous plane surface per unit volume, they oifer a minimum ofresistance to the Wind. Consequently the supporting masts require aminimum of bracing. In many uses, standard structural shapes are easilyadaptable.

Additional objects, features and advantages of the invention will beapparent from the following detailed description when read with theaccompanying drawings wherein:

FIGURE 1 is an elevational view of an antenna structure, in accordancewith a preferred embodiment of the invention, which permits theradiation of electromagnetic energy having a very large bandwidth;

FIGURE 2 is a cross-sectional view of the antenna structure taken alongthe line 2-2 of FIGURE 1 showing the central conductor as triangular incross-section;

FIGURE 3 is a cross-sectional view of another embodiment of theinvention in which the radiating conductor and the central conductorproject as squares on a plane perpendicular to the axis of the antenna;and

FIGURE 4 is an elevational view of a portion of an antenna structure inaccordance with another embodiment of the invention in which theribbonlike central conductor is a continuous sheet conductor rather thana mesh of conductors as shown in the embodiment of FIGURE 1.

Helical antenna systems may be grouped into two characteristic types.side-fire and end-fire.

In the side-fire type with which the subiect invention is concerned, theantenna system is vertically mounted with respect to the earth, and theradiation pattern may be either linearly or circularly polarized. Moreexactly, the volumetric radiation pattern of the side-fire type is asolid of revolution about the antenna axis of a directive lobe normal tothe axis. The radiation from an endfire helical antenna system isconcentrated along the axis of the helical antennas. The radiation mayalso be either circularly or linearly polarized.

The side-fire type is particularly useful in television broadcasting andin communication systems where receiving locations are in variousdirections. The end-fire 4; type is particularly useful for directedcommunications and in radar systems. i i

Side-fire types may be arrayed; that is, a number of helical antennasmay be supported end to end along a common axis. The side-fire typeswhen arrayed (stacked) produce a more concentrated radiation pattern indirections normal to the common axis.

Each helical antenna comprises a series of single turns or helices. Whenthe helical circumference is approximately some integral number ofoperating wavelengths, for example, two or four. wavelengths, and isdriven between a point on the helix and a concentric conducting mast,the major mode of radiation dominates; that is, the helical antenna isof the side-fire type. This follows because when the helical turns aresubstantially an integral number of operating wavelengths incircumference, the radiative currents of each turn are in phase at anydiscrete azimuth. Hence theyact in concert to cause side-fire radiation,somewhat similar to an in-phase fed echelon array of radiators.

A single bay antenna system for radiating electromagnetic energy inwhich two radiating conductors are disposed about a central conductor ofpolygonal cross-section, in accordance with the preferred embodiment ofthe invention, is shown in FIGURES 1 and 2. The antenna system generallycomprises a mast 20 carrying central conductors or ribbonlike elements22 and 24. The ribbonlike elements 22 and 24 are meshes of conductors.As shown in FIGURE 2, the cross-section of the most 20 is triangular andthe projection of the ribbonlike elements 22 and 24 on a planeperpendicular to the axis of mast 20 is a triangle. Insulativelysupported bythe mast 20 are radiating helical conductors 26 and 28. Afirst energization terminal 30 is coupled to the junction of the ends ofthe ribbonlike elements 22 and 24 at approximately the mid-point of themast 20. A second energization terminal 31 is coupled to the junction ofthe helical conductors 26 and 28 adjacent this mid-point. The first andsecond energization terminals 34 and 31 are respectively connected tothe outer and inner conductors of a coaxial line 36 which is connectedto one output stage of a transmitter 38. The antenna system will radiatesignal energy of a first kind; for example, the video signals of atelevision transmitter. However, the antenna system is self-diplexingand can simultaneously radiate, for example, both the audio and videosignals of a television transmitter. To perform this self-diplexing,third and fourth energization terminals 32 and 34 (FIG. 1) arerespectively connected to the ends of the helical conductors 26 and 28near the ends of the mast 20. The third and fourth energizationterminals 32 and 34" are con nected in parallel to the central conductorof the coaxial line 44) which is also connected to another output stageof the transmitter 38. Thus, if the transmitter 38 is a televisiontransmitter, the coaxial line would be coupled to the audio outputstage. It should be noted that although the third and fourthenergization terminals are shown near both ends of the mast 20, the mastmay extend beyond these points. More particularly, the third and fourthenergization terminals are near the electrical ends of the antenna.

The ribbonlike element 22 starts near the mid-point of the mast 2t) andextends as a plurality of axially progressive turns toward the top endof the mast 29. Similarly, the ribbonlike element 24 starts atthismid-point and extends as a plurality of axially progressive turns towardthe bottom of the mast 29. The ribbonlike elements 22 and 24 arepreferably joined at the mid-point. It should be noted that the turnsare spaced from each other to provide axial discontinuities whichsuppress the minor or coaxial mode of propagation, The helical conductor26 extends from the energization terminal 31 as a plurality of axiallyprogressive turns toward the top end of the mast 2t) and the helicalconductor 28 similarly extends to the bottom end of the mast 20. Each ofthe axially progressive turns is, preferably, substantially an integralnumber of operating wavelengths. The ribbonlike element 22 is in theradial shadow of the helical conductor 26. In other words, each elementof the helical conductor 26 is radially projectable on the ribbonlikeelement 22. The ribbonlike element 24 is similarly in the radial shadowof the helical conductor 28. Accordingly, the system may be consideredas a radiating transmission line system, the helical conductors 26 and28 being the radiating transmission lines and the ribbonlike elements 22and 24 the ground planes.

The mast 20 is fixed to a tower 54 braced by guy wires such as guy wire'56. In addition, a beacon light 58 and lightning rods 62 and 64 arepreferably provided at the top of mast 20'.

By referring to FIGURE 2, a more detailed understanding of the variouselements of the antenna system may be obtained. In particular, the mast28 includes three parallel upright members 42, 43 and 44 axiallyextending along the entire length. Bracing is provided by the struts orlateral support members 45, 46 and 47. It should be noted that thelateral support members 45, 46 and 47 form the sides of a triangle withthe upright members 42, 43 and 44 at the vertices. The ribbonlikeelement 24 which is identical to the ribbonlike element 22 is comprisedof a mesh of longitudinal conductors such as conductor 4'8 andtransverse conductors such as conductor 50. The portions of theribbonlike element 24 between adjacent upright members 42, 43 and 44 aresubstantially fiat.

The helical conductor 28 which is identical to the helical conductor 26is supported by insulative standofls such as standoff 52. Except for theportion near the energization terminal 31, the helical conductor 28projects as a circle on a plane perpendicular to the axis of ti e mast20. It is seen that the spacing between the helical conductor 28 and theribbonlike element 24 periodically varies between a maximum and aminimum. At the minimums there is a capacitive loading of the antenna.However, it should be noted that when particular non-azimuthally uniformradiation patterns are desired, this projection will be a closed curvehaving a variable radius of curvature such as an ellipse.

It should be noted that the rate of attenuation and the relativepercentages of modes of propagation are controlled by the effectiveradii of curvature of the antenna. In other words, when a conventionalhelical conductor is disposed around a cylindrical central conductor,the effective radii of curvature are the radius of the helix and theradius of the central cylindrical conductor. On the other hand, when ahelical conductor is developed about a conductor of polygonalcross-section, the effective radii of curvature are the radius ofcurvature of the helix and the radius of curvature of a circle havingapproximately the same area as the polygon. Similarly, if a helix ofnoncircular turns is employed as the radiatable conductor, its efiectiveradius of curvature would be approximately equal to the radius of acircle having an area equal to the projected area of the noncircularturn.

In any event, it has been found that the effective radius of the centralconductor should be greater than sixty percent of the effective radiusof the radiating conductor.

During operation as a television transmission antenna system the videosignal is fed from the transmitter 38 via the coaxial line 36 to theenergization terminals 3% and 31 where a first pair of waves ofelectromagnetic energy related to the video signal is launched on theantenna. One wave of electromagnetic energy travels between the helicalconductor 26 and the ribbonlike element 22 toward the top end of themast 20. Another wave of electromagnetic energy travels between thehelical conductor 28 and the ribbonlike element 24 toward the bottom endof the mast 2d. The major mode of propagation follows the axiallyprogressive turns of the helical conductors 26 and 28. As theelectromagnetic waves progress along these paths of travel there is aprogressive radiation into space W1 ich causes an attenuation of theenergy content of the waves. When each turn of the helical conductors 26and 28 is an integral number of operating wavelengths, the radiatedenergy is in phase at each azimuth position causing a reinforcement ofthe radiating energy.

At the same time, the audio signals are fed from the transmitter 38 viathe coaxial line 46} respectively to the energization terminals 32 and34. A second pair of electromagnetic waves related to the audio signalis launched on the antenna. One of these Waves travels between thehelical conductor 26 and the ribbonlike element 22 toward the center ofthe mast 20 and the other electromagnetic wave similarly travels betweenthe helical conductor 23 and the ribbonlike element 24 toward the centerof the mast 2%. Both waves progressively radiate.

Ordinarily, with side-fire helical antennas, there is a minor coaxialmode of propagation. However, because of the axial discontinuity of theribbonlike elements along any line parallel to the axis of the mast 2%,this coaxial mode is greatly suppressed so that a negligible amount ofthe available energy propagates in this mode. This results in a highdegree of isolation between the energization terminal 31 and theenergization terminals 32 and 34. This isolation is determined by thetotal radiative attenuation of the predominant helical mode.

Furthermore, because of the abrupt periodic discontinuities in theradial spacing between the helical conductors 26 and 2S and theribbonlike elements 22 and 24, there is a reactive loading etfect whichdispersively increases the phase-velocity versus frequency along thehelix to yield a broader bandwidth system.

Although for the low VHF television channels it is preferable to utilizea truly circular helical conductor, it has been found that with the highVHF television channels and with UHF television channels radiatingconductors having noncircular and even polygonal turns produce desirableradiation patterns. Accordingly, FIGURE 3 shows the cross-sectional viewof an antenna which is similar to the antenna of FIGURES 1 and 2 exceptthat the radiating conductor 28' and the ribbonlike element 24' each hasa projection of a square on a plane perpendicular to the supportingmast. It should be noted that other polygonal projections are equallysuitable. The use of other polygonal projections has certain advantageswhen chosen for certain applications. For example, in some cases apreferred directional horizontal pattern may be obtained more easily byusing any pattern distortion caused by the shape in complementaryfashion with other means for directionalizing, such as short stubsattached directly to the helix. Another advantage accrues when it isdesired to place the helix around a structural mast or tower which isalready in existence, and modifications to which are difiicult to make.

FIGURE 4 shows a portion of an antenna which is similar to the antennaof FIGURES 1 and 2 except that the ribbonlike element 24" is acontinuous sheet conductor instead of a mesh of conductors.

There has thus been shown improved antennas which have very broadbandwidth along with high operating efficiency. In particular, onefeature of the invention, by providing a discontinuously variablespacing between the radiating conductor and the central conductor,introduces periodic reactive loading which efiects a dispersive increasein phase velocity with frequency and accordingly enhances the frequencyresponse. The combination of this enhancement with proper radiationattenuation per turn permits construction of the antenna with a moreoptimum number of turns. Furthermore, according to another aspect of theinvention, the use of ribbonlike elements for the central conductorsgreatly suppresses the minor coaxial mode of propagation in the antennathus leading to higher isolation between the energization terminal andthe other end of the helix.

While a number of specific embodiments of the invention have beendescribed in detail, it should be apparent that many modifications andchanges may readily be made without departing from the spirit and scopeof the invention.

What is claimed is:

1. An antenna comprising a central conductor extending along the axis ofsaid antenna, the projection of said central conductor on a planeperpendicular to said axis being a polygon, said polygon havingsubstantially equal sides, a radiating conductor developed about saidcentral conductor as a plurality of axially progressive turns, a firstenergization means coupled to said central conductor, a secondenergization means coupled to said radiating conductor, and means forfeeding signal energy to said first and second energization means forradiation by said radiating conductor.

2. The antenna of claim 1 wherein said polygonal crosssection isa-triangle.

3. The antenna of claim 1 wherein said polvgonal crosssection is asquare.

4. An antenna comprising a central conductor extending along the axis ofsaid antenna, the projection of said central conductor on a planeperpendicular to said axis having a triangular cross-section, aradiating conductor developed about said central conductor in the formof a helix, a first energization means coupled to said centralconductor, a second energization means coupled to said radiatingconductor, and means for feeding signal energy to said first and secondenergization means for radiation by said radiating conductor.

5. An antenna comprising a central conductor extending along the axis ofsaid antenna, the projection of said central conductor on a planeperpendicular to said axis being a polygon, said polygon havingsubstantially equal sides, a radiating conductor developed about saidcentral conductor, said radiating conductor having a plurality ofaxially progressive turns of varying radius of curvature, a firstenergization means coupled to said central conductor, a secondenergization means coupled to said radiating conductor, and means forfeeding signal energy to said first and second energization means forradiation by said radiating conductor.

6. An antenna comprising a central conductor extending along the axis ofsaid antenna, the projection of said central conductor on a planeperpendicular to said axis being a polygon, a radiating conductordeveloped about said central conductor as a plurality of axiallyprogressive turns, a first energization means coupled to said centralconductor, a second energization means coupled to one end of saidradiating conductor, a third energization means coupled to the other endof said radiating conductor and means for feeding signal energy of afirst type to said first and second energization means for radiation bysaid radiating conductor and signal energy of a second type to saidfirst and third energization means for radiation by said radiatingconductor.

7. An antenna comprising a central conductor extending along the axis ofsaid antenna, the projection of said central conductor on a planeperpendicular to said axis being a polygon, a first radiating conductordeveloped about said central conductor as a plurality of axiallyprogressive turns extending toward one end of said central conductor, asecond radiating conductor developed about said central conductor as aplurality of axially progressive turns extending toward the other end ofsaid central conductor, a first energization means coupled to saidcentral conductor, a second energization means coupled to said first andsecond radiating conductors, and means for feeding signal energy to saidfirst and second energization means for radiation by said first andsecond radiating conductors.

8. An antenna comprising a central conductor extending along the axis ofsaid antenna, the projection of said central conductor on a planeperpendicular to said axis being a polygon, a first radiating conductordeveloped about said central conductor as a plurality of axiallyprogressive turns extending toward one end of said central conductor, asecond radiating conductor developed about said central conductor as aplurality of axially progressive turns extending toward the other end ofsaid central conductor, a first energization terminal coupled to saidcentral conductor, a second energization terminal coupled to the ends ofsaid radiating conductors remote from the ends of said centralconductor, third and fourth energization terminals respectivelyconnected to the ends of said radiating conductors adjacent the ends ofsaid central conductor, and means for feeding signal energy of a firsttype to said first and second energization terminals for radiation bysaid radiating conductors and signal energy of a second type to saidfirst, third and fourth energization terminals for radiation by saidradiating conductors.

9. An antenna comprising a central conductor extending alorn the axis ofsaid antenna, the projection of said central conductor on a planeperpendicular to said axis having a triangular cross-section, a firsthelical conductor developed in spaced relation about said centralconductor, said first helical conductor starting near the mid-point ofsaid central conductor and ending near one end of said centralconductor, a second helical conductor developed in spaced relation aboutsaid central conductor, said second helical conductor starting near themidpoint and ending near the other end of said central conductor, afirst energization terminal coupled to said central conductor, a secondenergization terminal coupled to the ends of said helical conductorsnear the mid-point of said central conductor, third and fourthenergization terminals respectively coupled to the ends of said helicalconductors near the ends of said central conductor and means for feedingsignal energy of a first frequency to said first and second energizationterminals for radiation by said helical conductors, and means forfeeding signal energy of a second frequency to said first, third andfourth energization terminals for radiation by said helical conductors.

10. An antenna comprising a ribbonlike conductor extending along theaxis of said antenna as a plurality of axially progressive turns, theprojection of said ribbonlike conductor on a plane perpendicular to saidaxis being a polygon, a radiating conductor extending along the axis ofsaid antenna as a plurality of axially progressive turns radiallydisplaced from said ribbonlike conductor with each portion of saidradiating conductor radially projectable on a portion of said ribbonlikeconductor, a first energization means coupled to said ribbonlikeconductor, a second energization means coupled to said radiatingconductor and means for feeding signal energy to said first and secondenergization means for radiation by said radiating conductor.

11. The antenna of claim 10 wherein said polygon is a triangle.

12. The antenna of claim 10 wherein said polygon is a square.

13. An antenna comprising a ribbonlike element of a substantially flatmesh of conductors extending along the axis of said antenna as aplurality of axially progressive turns, the projection of saidribbonlike element on a plane perpendicular to said axis being apolygon, a radiating conductor extending along the axis of said antennaas a plurality of axially progressive turns, said radiating conductorbeing radially displaced from said ribbonlike element with each portionof said radiating conductor being radially projectable on a portion ofsaid ribbonlike element, a first energization terminal coupled to saidribbonlike element, a second energization terminal coupled to saidradiating conductor and means for feeding signal energy to said firstand second energization terminals for radiation by said radiatingconductor.

14. An antenna comprising a ribbonlike element extending along the axisof said antenna as a plurality of axially progressive turns, theprojection of said ribbonlike element on a plane perpendicular to saidaxis being a polygon, a helical conductor extending along the axis ofsaid antenna radially displaced from said ribbonlilte element with eachportion of said helical conductor radially projectable on a portion ofsaid ribbonlike element, the projection of said helical conductor on aplane perpendicular to said axis being a similar polygon, a firstenergization terminal coupled to said ribbonlike element, a secondenergization terminal coupled to said helical conductor and means forfeeding signal energy to said first and second energization terminalsfor radiation by said helical conductor.

15. The antenna of claim 14 Wherein said polygons are triangles.

16. The antenna of claim 14 wherein said polygons are squares,

17. An antenna comprising a first ribbonlike element extending from apoint on the axis of said antenna in one direction as a plurality ofaxially progressive turns,

a second ribbonlilre element of a substantially flat mesh of conductors,said second ribbonlike element extending from said point in the oppositedirection as a plurality of axially progressive turns, the projection ofsaid first and second ribbonlike elements on a plane perpendicular tosaid axis being a polygon, a first helical conductor developed aboutsaid axis, said first helical conductor being radially displaced fromsaid first ribbonlike element with each portion of said first helicalconductor being radially projectable on a portion of said firstribbonlike element, a second helical conductor developed about saidaxis, said second helical conductor being radially displaced from saidsecond ribbonlike element with each portion of said second helicalconductor being radially projectable on a portion of said secondribboniike element, a first energization means coupled to said first andsecond ribbonlike elements, a second energization means coupled to saidfirst and second helical conductors, and means for feeding signal energyto said first and second energization means for radiation by said firstand second helical conductors.

18. An antenna comprising first and second ribbonlike elements, one endof each of said ribbonlike elements being joined at a point on the axisof said antenna, said ribbonlike elements extending from said point inopposite directions along said axis as axially progressive turns, theprojection of said first and second ribbonlike elements on a planeperpendicular to said axis being a polygon, first and second helicalconductors disposed about said axis, one end of each of said helicalconductors being joined at said point and extending in oppositedirections along said axis, said first helical conductor being radiallydisplaced from said first ribbonlike element with each element of saidfirst helical conductor being radially projectable on said firstribbonlike element, said second helical conductor being radiallydisplaced from said second ribbonlike element with each element of saidsecond helical conductor being radially projectable on said secondribbonlike element, a first energization terminal coupled to said firstand second ribbonlike elements, a second energization terminal coupledto the junction of said helical conductors, and means for feeding signalenergy to said first and second energization terminals for radiation bysaid helical conductors.

19. The antenna of claim 18 including third and fourth energizationterminals respectively coupled to the ends of said helical conductorsremote from said point, and means for feeding signal energy of a secondkind to said first, third and fourth energization terminals forradiation by said helical conductors.

20. An antenna comprising a mast, said mast including a plurality ofupright members with lateral support members, said upright membersdefining in a cross-sectional plane of said mast the vertices of apolygon, first and second ribbonlike elements of a substantially flatmesh of conductors disposed on said upright members, each of saidribbonlike elements starting near the mid-point of said mast andextending in opposite axial directions to- Ward the respective ends ofsaid mast, the portions of each of said ribbonlike elements betweenadjacent upright members defining a substantially straight line, firstand second helical conductors disposed about said mast, one end of eachof said helical conductors being joined together at said mid-point withsaid helical conductors extending from the junction toward opposite endsof said mast, said first helical conductor being radially displaced fromsaid first ribbonlike element with each element of said first helicalconductor being radially projectable on an element of said firstribbonlike element, said second helical conductor being radiallydisplaced from said second ribbonlike element with each element of saidsecond helical conductor being radially projectable on an element ofsaid second ribbonlike element, a first energization terminal coupled tosaid ribbonlike conductors, and a second energization terminal coupledto the junction of said helical conductors, and means for feeding signalenergy to said first and second energization terminals for radiation bysaid helical conductors.

21. The antenna of claim 20 including third and fourth energizationterminals respectively coupled to the ends of said helical conductorsremote from said junction, and means for feeding signal energy of asecond kind to said first, third and fourth energization terminals forradiation by said helical conductors.

References Cited in the tile of this patent UNITED STATES PATENTS2,871,478 Lander Jan. 27, 1959 2,945,227 Broussaud July 12, 1960 FOREIGNPATENTS 430,548 Great Britain Jan. 20, 1935 724,795 Great Britain Feb.23, 1955 1,160,874 France Mar. 10, 1958 OTHER REFERENCES The T.V.Helical Antenna Adapted to Structural Tower Shapes, by Fisk, IRETransactions on Broadcast Transmission Systems, PGBTS-l 1, September1958, pages 4 to 10,

